Human infection by the organism now known as Coccidioides immitis was first reported in 1892 by Posadas and Wernicke in Buenos Aires. These observers regarded the parasites as protozoa, but later (1896) Rixford and Gilchrist gave the organism the binominal designation of Coccidioides immitis, and Ophüls succeeded in obtaining pure cultures in 1900. Other cases have been recognized from time to time, and recently MacNeal and Taylor1 have collected twenty-four cases from the literature. In one of these reported by Brown, however (Case 18), the diagnosis was not confirmed culturally or by microscopic examination. All the reported cases except the first have occurred in the United States, and in a large proportion of them the infection can be traced to the San Joaquin Valley in California. The disease affects chiefly adult males, only one woman and one child being included in the cases observed. Only two patients are